1. Field of the Invention
This invention relates to a production method and a production system.
2. Description of the Prior Art
Production systems for successively producing works with a model-by-model transferring type of production line or a mixedly transferring type of production lines are known. In the model-by-model transferring type of production line, a production line is provided for each model. The mixedly transferring type of production line produces different models with one transferring production line.
FIG. 7A shows an example of the mixedly transferring type of the production line. In this example, it is assumed that brake parts are produced in the mixedly transferring production line. This production line successively executes processes of ball press-fitting assembling, motor-pump assembling, and solenoid assembling.
In this production system using a transferring type of production line, though production command is simple, a rate of operation in producing the work showing tact difference (time difference between respective processes) tends to be low. Moreover, the whole of the production line may stop when a severe trouble occurs at only a portion of the production line. Further, the rate of operation in producing a product is unstable and all processes may be affected by a neck process.
Another production system using block division type (Job Shop type) of production lines is known.
This production system includes independent production lines provided for respective processes such as the ball press-fit assembling, the motor-pump assembling, and the solenoid assembling. Thus, different processes are made at respective production lines, so that this production system is suited for producing a plurality of types of products in parallel.
In this block division type of production line, the operation interval can be adjusted every block unit (process) and modification of the system is possible every block unit. However, because these production lines are provided for producing a plurality of types of products, complicated production controlling is required. Thus, it is difficult to make the production commands for respective production lines.
More specifically, in the mixedly transferring block division type of production lines, the operator should make a production command every production line in consideration of tact differences, averaging the operation time of respective lines, calculating operation time, absorbing deviation in the number of requested products, and real time management of stocked products. This is very difficult.
FIG. 7B shows the processes in the mixedly transferring block division type of production lines. As shown in FIG. 7B, transferring a work from the previous process to another process is complicated every production line. That is, there are more than one previous or post processes for an intermediate line. In other words, an intermediate line has relation with more than one previous lines or post lines.
Moreover, to smoothly make process at each line, it is necessary to stock works to be processed at every production line. Thus, there is tendency that the number of stocked works increases in the prior art production lines.